Register for an account


Enter your name and email address below.

Your email address is used to log in and will not be shared or sold. Read our privacy policy.


Website access code

Enter your access code into the form field below.

If you are a Zinio, Nook, Kindle, Apple, or Google Play subscriber, you can enter your website access code to gain subscriber access. Your website access code is located in the upper right corner of the Table of Contents page of your digital edition.


X-Ray Vision Is So 20th Century

Researchers are building new systems that see through walls using radiation that's a lot safer than X-rays.

By Nick ZautraAugust 2, 2010 5:00 AM


Sign up for our email newsletter for the latest science news

Since the December “underwear bomb” plot, U.S. airports have rolled out a fleet of advanced imaging devices, including backscatter X-ray screeners and millimeter-wave body scanners. The gaze of all-seeing eyes could soon become even more penetrating, as physicists and engineers exploit new kinds of light that can see through barriers and clothing.

At the airport, the next generation of body scanners may rely on terahertz radiation, or T-rays. Unlike X-rays, T-rays are not energetic enough to strip electrons from atoms, making them safer for humans. They are also exceptionally sensitive to chemical structure, easily able to distinguish over-the-counter drugs from illegal substances. Before T-ray cameras and scanners can become a reality, however, researchers need to learn to control the radiation more precisely. Electrical engineer Qing Hu at MIT demonstrated a method to tune a terahertz laser by changing the diameter of the cavity emitting the rays, allowing him to finesse the beam to specific frequencies. And researchers at Texas A&M and Rice University are learning to control the rays by adjusting the temperature of a semiconductor film they pass through.

Other scanners may find better use in the field. At the University of Utah, engineer Neal Patwari and doctoral candidate Joey Wilson are using radio waves to see through obstacles. Their network of radio transceivers measures the signal strength to reveal the locations of people or objects in the area. The system can find targets in the dark and through walls, smoke, or trees. Patwari and Wilson are currently working to expand the transceivers’ range, currently 50 feet. For now the detector can follow only a single individual, Patwari says, “but we will soon be able to track multiple people or objects and tell the difference between them.” The technology could find applications in fire rescues, hostage situations, and border security.

    3 Free Articles Left

    Want it all? Get unlimited access when you subscribe.


    Already a subscriber? Register or Log In

    Want unlimited access?

    Subscribe today and save 70%


    Already a subscriber? Register or Log In